Eugenics is a social philosophy which advocates the improvement of human hereditary traits through various forms of intervention.
- But I see a third motive which unconsciously plays an important part; it is the idea of sacrifice. A lunatic may cause the mental and economic decay of a family and also ruin it morally. If healthy human beings make great sacrifices for the community and lay down their lives by order of the state, the insane person, if he could arouse himself mentally and make a decision, would choose a similar sacrifice for himself. Why should not the state be allowed to enact this sacrifice in his case and impose on him what he would want to do himself?"
- Nazi rationale for euthanizing the "unfit": Dr. Robert Servatius, attorney for Nazi war criminal Karl Brandt at Nuremberg, summing up the argument presented to the court in defense of the Nazi euthanasia program and Dr. Brandt's role therein. "Final Plea for Defendant Karl Brandt, by Dr. Servatius," July 14, 1947, "The Medical Case" in Trials of War Criminals Before the Nuernberg Military Tribunals under Control Council Law, (1949), No. 10, vol. II, October 1946 - April 1949, Nuenberg, U.S. Government Printing Office, Washington, D.C., p. 136.  This 15-volume series, also known as “The Green Series,” focuses on the 12 trials of almost 200 defendants   (Scholars have noted similarities between the language of Buck v. Bell and that of Dr. Robert Servatius, defense attorney for Dr. Karl Brandt at Nuremberg: "Brandt's attorney introduced documents quoting extensively from the eugenics literature. He cited Harry Laughlin's 1914 proposal calling for the sterilization of fifteen million Americans and also quoted a translation of the Buck v. Bell opinion from a German text on eugenics. Brandt's defense of Nazi experiments resulting in the death of concentration camp prisoners seemed to echo the Holmes opinion. Other Nuremberg defendants also cited Buck, and a translation of the Holmes opinion appeared again as a defense example in the exhibit 'Race Protection Laws of other Countries'." Three Generations, No Imbeciles: Eugenics, the Supreme Court, and Buck V. Bell, 2008, Paul A. Lombardo, Johns Hopkins University Press, ISBN 0801898242 ISBN 9780801898242 p. 239. ) See also: War Against the Weak: Eugenics and America's Campaign to Create a Master Race, Edwin Black, Dialog Press; 2003, expanded edition, 2012, ISBN 0914153293 ISBN 9780914153290 
- We civilised men do our utmost to check the process of elimination; we build asylums for the imbecile, the maimed, and the sick .... There is reason to believe that vaccination has preserved thousands... Thus the weak members of civilised societies propagate their kind. No one who has attended to the breeding of domestic animals will doubt that this must be highly injurious to the race of man. It is surprising how soon a want of care, or care wrongly directed, leads to the degeneration of a domestic race; but excepting in the case of man itself, hardly any one is so ignorant as to allow his worst animals to breed.
- Charles Darwin, 1871 (p. 501). The Descent of Man, and Selection in Relation to Sex. London: MacMillan.
- But if you can breed cattle for milk yield, horses for running speed, and dogs for herding skill, why on Earth should it be impossible to breed humans for mathematical, musical or athletic ability? Objections such as "these are not one-dimensional abilities" apply equally to cows, horses and dogs and never stopped anybody in practice. I wonder whether, some 60 years after Hitler's death, we might at least venture to ask what the moral difference is between breeding for musical ability and forcing a child to take music lessons. Or why it is acceptable to train fast runners and high jumpers but not to breed them. I can think of some answers, and they are good ones, which would probably end up persuading me. But hasn't the time come when we should stop being frightened even to put the question?
- Richard Dawkins, From the Afterword, The Herald Scotland, (November 20, 2006) 
- Eugenics was not inspired by Darwin's natural selection but by ancient agricultural ARTIFICIAL selection. Eugenics is UNnatural selection.
- One of the effects of civilisation is to diminish the rigour of the application of the law of natural selection. It preserves weakly lives that would have perished in barbarous lands.
- Francis Galton, 1865. Hereditary talent and character. MacMillan's Magazine, 12, 157-166; 318-327.
- There is a steady check in an old civilisation upon the fertility of the abler classes: the improvident and unambitious are those who chiefly keep up the breed. So the race gradually deteriorates, becoming in each successive generation less fit for a high civilisation.
- Francis Galton, 1869 (p.414). Hereditary Genius. London: MacMillan.
- I like Scandinavians, skiing, swimming and socialists who realize it is our business to promote social progress by peaceful methods. I dislike football, economists,
eugenicists, Fascists, Stalinists, and Scottish conservatives.
- Lancelot Hogben, in Stanley J. Kunitz, and Howard Haycraft,
Twentieth Century Authors, A Biographical Dictionary of Modern Literature, (Third Edition). New York, The H.W. Wilson Company, 1950, (pp. 658–59)
- All practices aimed at eugenics, any use of the human body or any of its parts for financial gain, and human cloning shall be prohibited.
- In the same way as the state demands the death of its best men as soldiers, it is entitled to order the death of the condemned in its battle against epidemics and diseases. No antique sacrifices to gods and demons are demanded any longer, only a well considered expiation as a help for the community and indeed exclusively in its interest.
- Trials of war criminals before the Nuremberg Military Tribunals under Control Council Law no. 10, Nuremberg, October 1946-April, 1949, Volume 1, U.S. Government Printing Office, 1949, p. 989.  (Jonathan P. Spiro notes that "The lawyer for Dr. Karl Brandt similarly (and repeatedly) argued that the life of the individual was expendable if it helped ensure the continued existence of the community....And in words that were remarkably similar to those of Oliver Wendell Holmes in Buck v. Bell, justified Nazi eugenics..." Defending the Master Race: Conservation, Eugenics, and the Legacy of Madison Grant, 2008, Jonathan Peter Spiro, University of Vermont Press, ISBN 1584657154 ISBN 9781584657156 p. 381. )
- Birth control and abortion are turning out to be great eugenic advances of our time. If they had been advanced for eugenic reasons, it would have retarded or stopped their acceptance.
- Frederick Osborn (1889-1981), American Eugenics Society (AES) speech, 1974, quoted in Margaret Sanger's Eugenic Legacy: The Control of Female Fertility (2005), Angela Franks, McFarland & Co., Jefferson, North Carolina, ISBN 0786420111 ISBN 9780786420117 ch.2, Eugenics as the Control of Births, pp. 65, 83.,  Citing, Frederick Osborn, "Notes on 'Paradigms or Public Relations: The Case of Social Biology,'" 2, 1/25/74, from FO papers, Notes on "Paradigms" folder. (see Franks, p. 270, n. 2, & p. 273, n. 105). 
- While modern social conditions are removing the crude physical checks which the unrestrained struggle for existence places on the over-fertility of the unfit, they may at the same time be leading to a lessened relative fertility in those physically and mentally fitter stocks, from which the bulk of our leaders have hitherto been drawn.
- Karl Pearson, 1901. National Life from the Standpoint of Science. London, Methuen.
- The only remedy, if one be possible at all, is to alter the relative fertility of the good and the bad stocks in the community.
- Karl Pearson, 1903. On the inheritance of the mental and moral characters in man. Journal of the Anthropological Institute of Great Britain and Ireland. 33, 179-237.
- [T]he campaign for Birth Control is not merely of eugenic value, but is practically identical in ideal, with the final aims of Eugenics.
- Eugenics is dead.
- Daniel Kevles, 1985. In the Name of Eugenics. New York: A. A. Knopf.
- To aid the bad in multiplying is, in effect, the same as maliciously providing for our descendants a multitude of enemies. Institutions which 'foster good-for-nothings' commit an unquestionable injury because they put a stop to that natural process of elimination by which society continually purifies itself.
- Herbert Spencer, 1874. Study of Sociology. London: MacMillan.
- We have seen more than once that the public welfare may call upon the best citizens for their lives. It would be strange if it could not call upon those who already sap the strength of the State for these lesser sacrifices, often not felt to be such by those concerned, in order to prevent our being swamped with incompetence. It is better for all the world, if instead of waiting to execute degenerate offspring for crime, or to let them starve for their imbecility, society can prevent those who are manifestly unfit from continuing their kind....Three generations of imbeciles are enough.
- In one of my last conversations with Darwin he expressed himself very gloomily on the future of humanity , on the ground that in our modern civilisation natural selection had no play and the fittest did not survive... It is notorious that our population is more largely renewed in each generation from the lower than from the middle and upper classes.
- Alfred Russel Wallace, 1890. Human selection. Popular Science Monthly 38: 90-102.
- … no man shall be subjected to any sort of mutilation or sterilisation except with his own deliberate consent, freely given.
- H. G. Wells, The Rights of Man, or what are we fighting for?, (1940)